The relationship between MMPs and pH in whole saliva of radiated head and neck cancer patients

Radiation-associated changes in saliva composition of head and neck cancer patients: A systematic review

Xerostomia is a common radiation-associated toxicity in patients with head and neck cancer. Although several studies examined the decrease in saliva production due to radiotherapy (RT) and investigated the factors associated with this side effect, little is known about the change in radiation-associated saliva composition. This systematic review is the first to summarize existing data and give an overview of the change in pH/buffer capacity, electrolytes, proteins, enzymes, and mucins due to radiation to the salivary glands. Literature search was performed in PubMed and Embase with 47 articles finally eligible for the review, analyzing the saliva composition at several time points before, during and/or after RT, or comparing findings in irradiated patients to a healthy control group. Overall, RT leads to a substantial decrease in salivary pH and buffer capacity. For sodium, chloride and calcium ion, as well as amylase, an increased concentration or activity during RT was reported in most of the studies, followed by a subsequent decrease either already during RT or after the end of treatment. Different trends have been described for the total protein concentration during and after RT. Lactoferrin, however, increased considerably, especially in the first phase of RT. Mucin 5B (MUC5B) concentrations showed a slight increase during RT and concentrations around baseline values again six months post-radiotherapy.

Evaluation of Alteration in Oral Microbial Flora Pre- and Postradiation Therapy in Patients with Head and Neck Cancer

Introduction:

For decades now, head and neck cancer (HNC) remains to be one of the deadliest; per se the treatment for the same has been evolving for the past years. Radiation therapy (RT) has been one among the various treatment modalities adopted to treat HNC. The fact that RT can affect the quality of life in these patients cannot be denied. In patients with HNC, these can bring about a wide array of lesions in oral cavity and its associated structures as these areas are invariably affected due to exposure to radiation as such. These include alteration in salivary parameters, changes in microbial flora, and occurrence of radiation caries.

Aim:

In our study we aimed at assessing the alteration in oral microbial flora inclusive of Streptococcus mutans and Lactobacillus colony count before and after RT.

Materials and Methods:

Saliva and plaque samples were collected from patients with HNC, who were prescribed to undergo intensity-modulated radiation therapy (IMRT) amounting to a mean radiation dosage of 60 Gy units. The aforementioned samples were collected at three different intervals, before, immediately after, and 6 months after RT. The samples were cultured in selective media in three different dilutions (1:10, 1:100, and 1:1000). Following with colony counting is carried out using a standardized colony counter.

Conclusion:

The results showed a significant alteration in microbial flora pre- and post-RT. Individual parameters do not show a single stand in causing these changes. Moreover, these changes seem to have earned a multifactorial contribution.

Influence of povidone-iodine on micro-tensile bonding strength to dentin under simulated pulpal pressure

Background

Previous studies had reported that bond strength deteriorate over time following the dentin surface pretreatment with chlorhexidine. Therefore, further investigations are needed to evaluate the effect of other materials such as povidone iodine.

The purpose of this study was to investigate the effects of 10% povidone-iodine pretreatment on the resin-dentin micro-tensile bond strength of a single bond adhesive system in permanent teeth over time, and compare it with 2% chlorhexidine.

Methods

Flat dentin surfaces were prepared in 63 extracted permanent teeth. Teeth were randomly assigned to a 10% povidone-iodine pretreatment, a 2% chlorhexidine pretreatment, or a control group. Composite resin blocks were built up over treated surfaces under pulp pressure simulation. The prepared specimens were assigned to three storage time, 24 h, 1 week, and 2 months. Samples were vertically sectioned to obtain specimens of 0.7 to 1.2 mm² cross-sectional area.

Results

No significant reduction of bond strength of povidone iodine group was found among the three storage times (p = 0.477). A significant reduction of bond strength for both chlorhexidine and control groups was found in the three storage times (p <  0.001).

Conclusion

Povidone iodine pretreatment of etched dentin was effective in reducing the loss of bond strength over time, while the chlorhexidine pretreatment and negative control showed significant deterioration in micro-tensile bond strength over time in permanent teeth.

Mucosal microflora in head and neck cancer patients

OBJECTIVE

To analyse the tongue and buccal microflora prospectively in head and neck cancer patients treated with radiation therapy (RT).

METHODS

In 33 dentate patients, microbial samples from the tongue and buccal mucosa were collected pretreatment, during treatment, and 6 months, 1 year and 2 years post-treatment. Microorganisms associated with oral health and oral disorders were analysed using cultivation technique. Oral mucositis was scored at the appointment during treatment.

RESULTS

Compared with pretreatment, lactobacilli and Candida increased on the tongue, while streptococci and Neisseria decreased during treatment. Two years post-treatment, Neisseria and Prevotella were decreased and Candida increased. On the buccal mucosa, an increased growth of lactobacilli and increased detection frequencies of the opportunistic bacteria Staphylococcus aureus, Gram-negative enteric rods and enterococci were seen during treatment compared with pretreatment. Seventy per cent showed severe mucositis during treatment. Two years post-treatment the total count as well as streptococci, Neisseria and Fusobacterium nucleatum were decreased and lactobacilli increased compared with pretreatment.

CONCLUSION

Despite improvements in treatment for cancer in the head and neck region, microorganisms associated with oral health decrease during treatment and mucosal pathogens increase. Two years post-treatment, levels of acid-tolerant (lactobacilli and Candida) were increased, while acid-sensitive microorganisms (Neisseria and F. nucleatum) were decreased, plausibly due to persisting decreased salivary secretion rate.

Use of Surrogate Samples to Monitor pH During High dose Methotrexate Therapy

High dose methotrexate (Mtx) therapy is commonly used in hemato-oncological practice. Alkalization of urine is a part of high dose methotrexate therapy for preventing crystallization in urine to avert renal insufficiency. Alkalization is monitored by urine pH at regular intervals. Oral pH has occasionally been used as a surrogate for oral mucositis. To compare and correlate pH of various body secretions (venous blood, oral salivary, lacrimal and urine) among patients undergoing alkalization with intravenous sodium bicarbonate during high dose methotrexate therapy. A prospective single center study in patients with hematological malignancies receiving Mtx > 1.5 g/m² over 4-24 h. Patients were assessed for pH (from all 4 body fluids) at regular time intervals (q8 h) starting 6 h-prior and 48 h-post initiation of Mtx therapy. Mean pH of urine/oral was compared to surrogate samples. The mean oral pH was 6.9 (SD 0.65), the mean urinary pH was 7.59 (SD 0.773) the mean pH by venous blood gas analysis (venous pH) was 7.388 (SD 0.059), the mean lacrimal pH was 7.4536 (SD 0.527). Repeated measures ANOVA suggests that pH of different body fluids differ and cannot be used interchangeably [F (2.417, 309.361) = 54.89, p < 0.0005]. There was no statistically significant correlation between any other pair of assessed body fluids. On paired t test only the means of venous pH and urinary pH did not differ statistically (p 0.056). Venous pH significantly correlated with urinary pH but the strength of correlation was weak (r 0.184; p 0.037). pH of different body fluids is statistically different even when sampled simultaneously thus the pH of one fluid cannot be substituted for other. Based on this study we cannot substitute urinary pH with any other body fluids presently in patients undergoing high dose methotrexate and alkalization except in rare circumstances when venous pH can be used as a poor surrogate for urinary pH in situations where urinary pH cannot be monitored due to any reason. There was no surrogate for oral pH among the studied body fluids.

Dental Plaque pH and Micro-organisms during Hyposalivation

We have previously reported that minor gland and whole saliva flow rates and salivary proteins showed differences in individuals with primary Sjögren’s syndrome or head and neck radiation therapy, compared with controls ( Eliasson et al., 2005 ). We now hypothesize that pH and number of acidogenic micro-organisms in dental plaque as well as saliva buffering capacity also differ in these individuals. Plaque pH was measured by the microtouch method up to 60 min after a sucrose rinse. Plaque collected from the same sites was analyzed for counts of total and acidic micro-organisms. Compared with their controls, the irradiated group but not the Sjögren’s syndrome group displayed significantly lower plaque pH, increased numbers of lactobacilli and Candida species, as well as reduced buffering capacity. Stepwise regression tests suggested that the buccal minor-salivary-gland secretion rate in the test groups and counts of mutans streptococci in the controls were of significant importance for dental plaque pH.

Collagen Degradation by Host-derived Enzymes during Aging

Incompletely infiltrated collagen fibrils in acid-etched dentin are susceptible to degradation. We hypothesize that degradation can occur in the absence of bacteria. Partially demineralized collagen matrices (DCMs) prepared from human dentin were stored in artificial saliva. Control specimens were stored in artificial saliva containing proteolytic enzyme inhibitors, or pure mineral oil. We retrieved them at 24 hrs, 90 and 250 days to examine the extent of degradation of DCM. In the 24-hour experimental and 90- and 250-day control specimens, we observed 5- to 6-μm-thick layers of DCM containing banded collagen fibrils. DCMs were almost completely destroyed in the 250-day experimental specimens, but not when incubated with enzyme inhibitors or mineral oil. Functional enzyme analysis of dentin powder revealed low levels of collagenolytic activity that was inhibited by protease inhibitors or 0.2% chlorhexidine. We hypothesize that collagen degradation occurred over time, via host-derived matrix metalloproteinases that are released slowly over time.

Salivary flow rate and biochemical composition analysis in stimulated whole saliva of children with cystic fibrosis

OBJECTIVE

It is recognized that cystic fibrosis (CF) patients present a risk for oral diseases, since it affects exocrine glands, and the treatment consists of a carbohydrate-rich diet. Recognizing the protective function of saliva on maintaining oral health, the aim of the study was to evaluate salivary parameters in stimulated whole saliva from children with CF.

METHODS

A case-control study was conducted comparing stimulated whole saliva of healthy (n=28; control group) and CF children (n=21; experimental group). Salivary flow rate, initial pH, buffer capacity (total and in each range of pH), total protein and sialic acid (total, free, and conjugated) concentration, α-amylase and salivary peroxidase activities were evaluated. Data were compared by two-tailed Student t test (95% CI; p ≤ 0.05).

RESULTS

CF patients presented a significant reduction in salivary parameters compared with the control group (p ≤ 0.05): salivary flow rate (36%), buffer capacity (pH range from 6.9 to 6.0), sialic acid concentration (total 75%, free 61%, and conjugated 83%); α-amylase and salivary peroxidase activities (55%). Additionally, a significant increase in total protein concentration (180%) of stimulated whole saliva from CF patients was verified compared with the control group (p ≤ 0.05).

CONCLUSION

Children with CF presented significant changes in salivary composition, including salivary flow rate, buffering capacity and protective proteins of the oral cavity, compared with children without CF.

Caries correlates strongly to salivary levels of matrix metalloproteinase-8

The caries process in dentin involves the degradation of both mineral and organic matrix. The demineralization has been demonstrated to be caused by bacterial acids. However, the collagen degradation is considered to be initiated by endogenous proteolytic enzymes, mainly collagenolytic matrix metalloproteinases (MMPs). This paper aims to relate salivary MMP-8 (or salivary collagenase-2) and tissue inhibitor of MMP (TIMP-1) levels to manifest caries in a large number of subjects. A random sample of 451 adults (aged 18-87 years) living in the south of Sweden was included in this study. Standard clinical examinations were performed, and stimulated saliva was collected and analyzed for concentrations of MMP-8, TIMP-1 and total protein, using an immunofluorometric assay, an enzyme-linked immunosorbent assay and the Bradford assay, respectively. Salivary numbers of mutans streptococci and lactobacilli were determined using a chair-side kit. Subjects with manifest caries lesions presented with elevated levels of MMP-8 (p < 0.001) as well as total protein, MMP-8/TIMP-1 ratio, bleeding on probing and plaque index (p = 0.05) compared with subjects without manifest caries. Multiple linear regression analysis with caries as the dependent variable revealed MMP-8 as the only significant explanatory variable (p < 0.001). TIMP-1 was not significant in any case. Using MMP-8 as the dependent variable revealed total protein concentration, caries lesions (p ≤ 0.001) and salivary secretion rate (p = 0.05) as explanatory variables. In conclusion, our data reveal that subjects with manifest caries lesions have elevated levels of salivary MMP-8 relative to subjects with no caries lesions.

Saliva and dental erosion

Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear.

OBJECTIVE

This review discusses the role of salivary factors on the development of dental erosion.

MATERIAL AND METHODS

A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party.

RESULTS

Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion.

CONCLUSIONS

Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

Free energy calculations on snake venom metalloproteinase BaP1

BaP1 is a snake venom metalloproteinase from the venom of Bothrops asper, showing high structural homology with the catalytic domain of human adamalysins and matrix metalloproteinases. It induces the release of cytokines, like interleukin-1 and tumor necrosis factor alpha. Recently, the high-resolution crystal structure of BaP1 with a bound inhibitor became available, representing an interesting model concerning inhibitor design for medicinally important metalloproteinases such as tumor necrosis factor alpha-converting enzyme and MMP13. We here use computational modeling to gain a better understanding about the binding properties of various ligands to BaP1, with a focus on computing ligand binding free energies. The obtained results should be of general significance for future research on medicinally important metalloproteinases. We have investigated the binding of the original inhibitor in detail and calculated its binding strength using MMP/GBSA free energy calculations. Additionally, the binding strengths of alternative ligands have been computed, and two of them are predicted and experimentally verified to strongly inhibit the enzyme. A suggestion for chemical modifications of BaP1 inhibitors could be made to guide future synthesis efforts. Furthermore, a contribution to the proteolytic reaction mechanism of metzincins is given. The pK value of the catalytically active glutamic acid residue 143 has been found to be significantly raised when compared with a free glutamate side chain. Calculations on other matrix metalloproteinases confirmed that this is not confined to BaP1, but seems to be a common feature of metzincins.

Matrix metalloproteinases: key regulators in the pathogenesis of chemotherapy-induced mucositis?

Chemotherapy is an effective anticancer treatment; however, it induces mucositis in a wide range of patients. Mucositis is the term used to describe the damage caused by radiation and chemotherapy to mucous membranes of the alimentary tract. This damage causes pain and ulceration, vomiting, bloating and diarrhoea, depending on the area of the alimentary tract affected. Although treatment is available for a small subset of patients suffering from mucositis, the majority rely on pain relief as their only treatment option. Much progress has been made in recent years into understanding the pathobiology underlying the development of mucositis. It is well established that chemotherapy causes prominent small intestinal and colonic damage as a result of up-regulation of stress response genes and pro-inflammatory cytokines. However, better understanding of the mediators of this damage is still required in order to target appropriate treatment strategies. Possible mediators of mucositis which have not been well researched are the matrix metalloproteinases (MMPs). MMPs have been shown to function in several of the pathways which are known to be up-regulated in mucositis and contribute to tissue injury and inflammation in many pathological conditions. This prompts the consideration of MMPs as possibly being key mediators in mucositis development.

The role of matrix metalloproteinases in the oral environment

This review focuses specifically on matrix metalloproteinases (MMPs) and their role in physiological and pathological extracellular matrix (ECM) remodeling and degradation processes in the oral environment. A group of enzymes capable of degrading almost all ECM proteins, MMPs contribute to both normal and pathological tissue remodeling. The expression of different MMPs may be upregulated in pathological conditions such as inflammation and tumor invasion. The balance between activated MMPs and tissue inhibitors of metalloproteinases (TIMPs) controls the extent of ECM remodeling. Prior to mineralization, MMPs may participate in the organization of enamel and dentin organic matrix, or they may regulate mineralization by controlling the proteoglycan turnover. There is evidence indicating that MMPs could be involved in the etiology of enamel fluorosis and amelogenesis imperfecta. They seem to play a part in dentinal caries progression, since they have a crucial role in dentin collagen breakdown in caries lesions. MMPs have been identified in pulpal and periapical inflammation and are strongly correlated with periodontal diseases, since they are the major players in collagen breakdown during periodontal tissue destruction. The use of MMP inhibitors could help the prevention and treatment of many MMP-related oral diseases.

Molecular alterations of parotid saliva in infantile chronic recurrent parotitis

Infantile chronic recurrent parotitis (ICRP) is an insidious disease whose etiopathogenesis remains an enigma. Alterations in the physical appearance of parotid saliva from ICRP patients have been frequently reported. However, sialochemical studies in regard to ICRP are very rare. The aim of this study was to determine whether saliva of ICRP patients presents major physicochemical and biochemical alterations compared with saliva from paired healthy controls. Parotid, whole, and submandibular/sublingual saliva was collected at an asymptomatic stage from 33 ICRP patients (5-16 y old, both sexes) and from 33 sex- and age-matched healthy controls. Saliva was analyzed for protein concentration, mode of protein diffusion on cellulose membranes, unidimensional sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis protein profiles and zymographic profiles of metalloproteinase 2 (MMP-2) and metalloproteinase 9 (MMP-9). Parotid saliva of ICRP patients showed an increased protein concentration, altered mode of protein diffusion, a higher frequency of polypeptide bands of 43, 37, 33, 29, 26, 16, and 10 kD, higher asymmetry in the polypeptide profiles of both contralateral parotid saliva, and an increase in the frequency of MMP-2 and MMP-9. Parotid saliva of patients with ICRP is molecularly altered with respect to normal saliva. Some of the molecular differences could be related to the etiopathogenesis of the disease.

Levels of matrix metalloproteinase-2, −9 and −8 in the skin, serum and saliva of smokers and non-smokers

Smoking induces skin ageing, affects wound healing and inflammatory responses in skin and mucous membranes but the mechanisms behind these adverse effects of smoking are not clear. The objective was to elucidate the mechanisms of smoking-related tissue damage, by comparing the levels of matrix metalloproteinases (MMPs) -2, -9, and -8 in the skin, serum and saliva of smokers and non-smokers. The study population consisted of 47 current smokers and 51 non-smokers, all males of Finnish origin. Skin samples from the upper inner arm were frozen in liquid nitrogen. Levels of MMP-2 and MMP-9 protein in the skin were assessed by zymography and MMP-8 isoforms were determined by Western blotting. From the serum samples, MMP-2 and MMP-9 were assessed by zymography and MMP-8 levels by time-resolved immunofluorometric assay (IFMA). From the salivary samples, MMP-8 levels were analysed by IFMA and MMP-9 levels by capture activity assay. In skin tissue, lower levels of both the pro and active forms of MMP-9 and of the active forms of MMP-8 were found in the smokers compared to the non-smokers. In serum, higher levels of proMMP-2 and proMMP-9 were found in the smokers compared to the non-smokers (P=0.001 and P<0.001, respectively), whereas MMP-8 levels did not differ significantly between the groups. Active forms of MMP-9 and MMP-2 could not be found in serum. In saliva, the amount of total MMP-9 was significantly lower in the smokers (156.0 U/ml) compared to the non-smokers (223.9 U/ml, P=0.032), whereas the levels of MMP-8 or active MMP-9 did not differ significantly between the groups. We conclude that smoking alters the levels of matrix metalloproteinases in skin tissue, serum and saliva, which may affect the turnover of extracellular matrix of skin even though the clinical impact of our findings is not clear.